Applications of CAD Systems

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Applications of CAD Systems

• Chapter 11 Numerical Control
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• Computerized process planning without human
  intervention realized by adding Numerical Control
  (NC) capabilities to machine tools.
• Numerical Control refers to the use of coded
  numerical information in the automatic control of
  equipment positioning and have to do with motion
  (of cutting tools or the part against a rotating
  tool), positioning, inserting etc.
• The production steps stored in a Part Program.

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?e??e??µe?a

• Introduction
• Hardware Configuration of an NC Machine Tool
• Types of NC System
• NC/CNC/DNC
• Basic Concepts for Part Programming
• Manual Part Programming
• Computer Assisted Part Programming

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• Introduction
• Hardware Configuration of an NC Machine Tool
• Types of NC System
• NC/CNC/DNC
• Basic Concepts for Part Programming
• Manual Part Programming
• Computer Assisted Part Programming

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Introduction / History

• In 1940s John Parsons devised a method for
  manufacture of smooth shapes, relied on recording
  the location of the center of large number of
  holes and feeding this information to a machine
  tool to drive the cutter. The Air Corps was
  impressed by the idea and the task was
  subcontracted to the Servomechanisms Laboratory
  of MIT
• In 1952 a modified 3-axis Cincinnati Hydrotel
  milling machine was demonstrated by MIT, the term
  numerical control was coined

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Introduction

• According to Electronic Industries Association
  (EIA)
• Numerical Control is a system in which actions
  are controlled by direct insertion of numerical
  data at some point. The system must automatically
  interpret at least some portion of this data.
• The part program is a set of statements that a
  machine control system can interpret and
  converted them into signals that move the
  spindles and drive the machine tool
• Today the part program can be generated directly
  from the CAD database by NC software and then can
  be the input for a NC machine tool

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?e??e??µe?a

• Introduction
• Hardware Configuration of an NC Machine Tool
• Types of NC System
• NC/CNC/DNC
• Basic Concepts for Part Programming
• Manual Part Programming
• Computer Assisted Part Programming

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Hardware Configuration of an NC Machine Tool
A typical NC machine tool contains the Machine
Control Unit (MCU) and the machine tool itself.

• The MCU includes
• the Data Processing Unit (DPU) and
• the Control Loop Unit (CLU)

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Hardware Configuration of an NC Machine Tool

• DPU reads the part program, decodes it, processes
  the information and passes it to the CLU
• CLU convert the information to control signals
  and drives the mechanism, receives feedback
  (about position and velocity) and instructs DPU
  to read new instructions
• Axis of a machine tool is defined as a path along
  which relative motion between the cutting tool
  and the workpiece occurs and a machine can have
  more than one axis.

10
?e??e??µe?a

• Introduction
• Hardware Configuration of an NC Machine Tool
• Types of NC System
• NC/CNC/DNC
• Basic Concepts for Part Programming
• Manual Part Programming
• Computer Assisted Part Programming

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Types of NC System Used

• Point-to-Point NC controllers PTP
• When the path of the tool relative to the work
  piece is not important, maybe when the tool is
  not in contact with the workpiece
• Contouring (continuous) NC systems
• When the motion of the tool relative to the part
  being machined is important

12
?e??e??µe?a

• Introduction
• Hardware Configuration of an NC Machine Tool
• Types of NC System
• NC/CNC/DNC
• Basic Concepts for Part Programming
• Manual Part Programming
• Computer Assisted Part Programming

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NC/CNC/DNC

• Third generation of machine tools uses integrated
  circuits and memory technology wildly used in
  computer hardware
• Computer Numerical Control (CNC, about 1970)
  program needs loading into the MCU once, the
  controller resembles a personal computer, it is a
  special-purpose computer for control of machine
  tools with CPU, ROM, RAM, hard disk communication
  ports, key pad, display monitor etc.
• Today PC-based NC are available which use
  general-purpose PC with servo-control board.

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NC/CNC/DNC

• Direct Numerical Control is a system that uses a
  central computer to control several machines at
  the same time
• Distributed Numerical Control (DNC) the central
  computer downloads complete programs to the CNC
  machines, which can be workstations or PCs, and
  can get the information for the machine
  operations.
• The speed of the system is increased, large files
  can be handled and the number of machine tools
  used is expanded.

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Direct numerical control
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DNC
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?e??e??µe?a

• Introduction
• Hardware Configuration of an NC Machine Tool
• Types of NC System
• NC/CNC/DNC
• Basic Concepts for Part Programming
• Manual Part Programming
• Computer Assisted Part Programming

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Basic Concepts for Part Programming

• Part programming contains geometric information
  about the part and motion information to move the
  cutting tool with respect to the workpiece
• The first thing to be defined is the
• Coordinate System and then some-one can continue
  with the Syntax of Part Programming

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Coordinate System

• Main 3 Axes forming a right-hand coordinate
  system, by convention z axis moves the cutting
  tool away from the workpiece, in details
• The z axis, parallel to the spindle for rotating
  workpiece, and parallel to the machine tool axis
  for rotating tool, as a milling, drilling, or
  boring machine
• The x axis, in the direction of the tool movement
  for the first case, and points to the right when
  some-one is facing the machine.

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Coordinate System

• There can be more axes because of secondary slide
  motions in addition to the primary x, y and z
  directions, and the rotary motions around axes
  parallel to x, y and z axes.
• These axes can be labeled u, v and w (for the
  first case) and a, b and c (for the second).
• The machine tools can be classified according to
  the number of axes they provide to control
  position and orientation. For example, there are
  2-axis, 3-axis and 5-axis milling machines.

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Syntax of Part Programming

• Various formats and well defined syntax with
  variations due to differences between machines
• Use of a sequence of blocks containing commands
  to set machine parameters as speed etc
• Each command has an identifying letter followed
  by an associated number

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Syntax of Part Programming

• Some identifying letters for the commands
• Sequence number (N code)
• Preparatory command (G code)
• Dimension words (X, Y, Z, A and B words)
• Feed commands (F code)
• Speed commands (S code)
• Tool selection (T code)
• Miscellaneous (M code)

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Syntax of Part Programming

• Formats for the commands arranged to form a
  block
• Fixed sequential format
• Block address format
• Tab sequential format
• Word address format
• For example N040 G00 X0 Y0 Z300 T01 M06
• N identifier number, G preparatory commands,
• X,Y and Z coordinates along the x, y and z axis
• T the tool number and M miscellaneous commands

26
?e??e??µe?a

• Introduction
• Hardware Configuration of an NC Machine Tool
• Types of NC System
• NC/CNC/DNC
• Basic Concepts for Part Programming
• Manual Part Programming
• Computer Assisted Part Programming

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Manual Part Programming

• Part program manuscript

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Manual Part Programming Example
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Manual Part Programming Answer

• N001 G91 EOB
• N002 G71 EOB
• N003 G00 X0.0 Y0.0 Z40.0 T0.1 M06 EOB
• N004 G01 X65.0 Y0.0 Z-40.0 F950 S717 M03 EOB
• N005 G01 X10.0 F350 M08 EOB
• N006 G01 X110.0 EOB
• N007 G01 Y70.0 EOB
• N008 G01 X-40.86 EOB
• N009 G02 X-28.28 Y0.0 I14.14 J5.0 EOB
• N010 G01 X-40.86 EOB
• N011 G01 Y-70.0 EOB
• N012 G01 X-75.0 Y0.0 Z40.0 F950 M30

30
?e??e??µe?a

• Introduction
• Hardware Configuration of an NC Machine Tool
• Types of NC System
• NC/CNC/DNC
• Basic Concepts for Part Programming
• Manual Part Programming
• Computer Assisted Part Programming

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Computer Assisted Part Programming

• The alternative to manual part programming is the
  use of high-level programming language, which
• Defines the geometry part in terms of basic
  geometry elements (points, lines )
• Instructs the machine about the cutting tool

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Computer Assisted Part Programming

• So the following procedures must be used to
  obtain the G-code
• The programmer identifies the part geometry,
  cutter motions, feeds, speeds and cutter
  parameters
• The programmer codes the part geometry, cutter
  motion, feed etc and this is the source using a
  programming language
• The source is then compiled to produce the
  machine independent list of cutter movements and
  other machine control information (the cutter
  location control data file or CL data file)
• The CL data are processed by post-processor to
  generate machine control data for the particular
  machine

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APT Language

• The most comprehensive and widely used language
  is Automatically Programmed Tool (APT) the
  first prototype of the APT system was developed
  at MIT in 1956.
• The APT statements belong to one of the five
  types
• Identification statements
• Geometry statements
• Motion statements
• Post-processor statements
• Auxiliary statements

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APT Language

• Geometry statements, the general form of geometry
  statement is
• Symbol geometry_word/descriptive data
• In the case of points
• P1 POINT/X, Y, Z
• P2 POINT/L1, L2
• P3 POINT/CENTER, C1
• P4 POINT/YLARGE, INTOF, L1, C1
• P5 POINT/XLARGE, INTOF, L1, C1
• P6 POINT/XLARGE, INTOF, C1, C1
• P7 POINT/YLARGE, INTOF, C1, C1

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APT Language

• In the case of lines
• L1 LINE/X1, Y1, Z1, X2, Y2, Z2
• L2 LINE/P1, P2
• L3 LINE/P1, PARLEL, P2
• L4 LINE/P1, PERPTO, L0
• L5 LINE/P1, LEFT, TANTO, C1
• L6 LINE/P1, RIGHT, TANTO, C1
• L7 LINE/LEFT, TANTO, C1, LEFT, TANTO, C2
• L8 LINE/LEFT, TANTO, C1, RIGHT, TANTO, C2
• L9 LINE/RIGHT, TANTO, C1, LEFT, TANTO, C2
• L10 LINE/RIGHT, TANTO, C1, RIGHT, TANTO, C2
• L11 LINE/P1, ATANGL, L0

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APT Language

• In the case of circles
• C1 CIRCLE/X, Y, Z, R
• C2 CIRCLE/CENTER, P1, RADIOUS, R
• C3 CIRCLE/CENTER, P1, TANTO, L0
• C4 CIRCLE/P1, P2, P3
• C5 CIRCLE/XSMALL, L1, XSMALL, L2, RADIOUS, R
• And the same with XLARGE, YLARGE or YSMALL
• In the case of planes
• PL1 PLANE/P1, P2, P3
• PL2 PLANE/PARLEL, PL0, XLARGE, D
• And the same with XLARGE, YLARGE, YSMALL, ZLARGE
  or ZSMALL

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APT Language

• Motion statements, with regard to point-to-point
  operation there are three motion statements for
  positioning the tool at a desired point
• FROM/point_location
• GOTO/point_location
• GODLTA/?x, ?y, ?z

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APT Language Example 1
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APT Language Answer

• P0 POINT/0.0, 3.0, 0.1
• P1 POINT/1.0, 1.0, 0.1
• P2 POINT/2.0, 1.0, 0.1
• FROM/P0
• GOTO/P1
• GODLTA/0, 0, -0.7
• GODLTA/0, 0, 0.7
• GOTO/P2
• GODLTA/0, 0, -0.7
• GODLTA/0, 0, 0.7
• GOTO/P0

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APT Language

• Other Motion statements
• GO/TO, Drive surface, TO Part surface, TO,
  Check surface
• Or
• GO/TO, Drive surface, TO Part surface,
  TANTO, Check surface
• And the same with PAST or ON instead of TO
• GOLFT/
• GORGT/
• GOUP/
• GODOWN/
• GOFWD/
• GOBACK/
• For example
• GO/TO, L1, TO, PS, TANTO, C1
• GO/PAST, L1, TO, PS, TANTO, C1

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APT Language Example 2
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APT Language Answer

• FROM/SP
• GO/TO, L1, TO, PS, ON, L4
• GORGT/L1, PAST, L2
• GOLFT/L2, PAST, L3
• GOLFT/L3, PAST, C1
• GOLFT/C1, PAST, L3
• GOLFT/L3, PAST, L4
• GOLFT/L4, PAST, L1
• GOTO/SP

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APT Language Example 3
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APT Language Answer

• FROM/SP
• GO/TO, L1, TO, PS, ON, L6
• GORGT/L1, PAST, L2
• GORGT/L2, TANTO, C1
• GOFWD/C1, TANTO, L3
• GOFWD/L3, PAST, L4
• GOLFT/L4, PAST, L5
• GOLFT/L5, PAST, L6
• GOLFT/L6, PAST, L1
• GOTO/SP

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APT Language

• Additional statements
• MACHIN/DRILL, 2
• COOLNT/
• For example COOLNT/MIST COOLNT/FLOOD COOLNT/OF
  
• FEDRAT/
• SPINDL/
• For example SPINDL/ON SPINDL/1250, CCLW
• TOOLNO/
• TURRET/
• END

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APT Language

• Other capabilities of APT, the macro facility,
  with use variable argument as in a FORTRAN
  subroutine, for example
• P0 POINT/0.0, 0.3, 0.1
• FROM/P0
• CALL/DRILL, X1.0, Y1.0, Z0.1, DEPTH0.7
• CALL/DRILL, X2.0, Y1.0, Z0.1, DEPTH0.7
• GOTO/P0
• when the definition of the macro DRILL is
• DRILL MACRO/X, Y, Z, DEPTH
• GOTO/X,Y,Z
• GODLTA/0,0, -DEPTH
• GODLTA/0,0, DEPTH
• TARMAC

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APT Language Example 4 (1/2)
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APT Language Example 4 (2/2)
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APT Language Answer (1/4)

• PARTNO PART11
• MACHIN/MILL, 3 machine selection
• CLPRINT prints out CL data file
• OUTTOL/0.002
• SP POINT/5,0,1
• P1 POINT/1,2,0.5
• P2 POINT/4,2,0.5
• P3 POINT/6,4,0.5
• P4 POINT/8,5,0.5
• P5 POINT/9,7,0.5
• P6 POINT/2,7,0.5
• PL1 PLANE/P1, P2, P3
• PS PLANE/PARALEL, PL1, ZSMALL, 0.5
• define part surface to be z 0

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APT Language Answer (2/4)

• C1 CIRCLE/CENTER, P4, RADIOUS, 1.0
• L1 LINE/P2, P3
• L2 LINE/P3, RIGHT, TANTO, C1
• L3 LINE/P5, LEFT, TANTO, C1
• L4 LINE/P5, P6
• L5 LINE/P6, P1
• L4 LINE/P1, P2
• MILL MACRO/CUT, SPIN, FEED, CLNT
• CUTTER/CUT
• FEDRAT/FEED
• SPINDL/SPIN
• COOLNT/CLNT
• FROM/SP

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APT Language Answer (3/4)

• FROM/SP
• GO/TO, L1, TO, PS, ON, L6
• GORGT/L1, TO, L2
• GORGT/L2, TANTO, C1
• GOFWD/C1, TANTO, L3
• GOFWD/L3, PAST, L4
• GOLFT/L4, PAST, L5
• GOLFT/L5, PAST, L6
• GOLFT/L6, PAST, L1
• GOTO/SP
• TERMMAC
• TURRET/4

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APT Language Answer (4/4)

• TURRET/4
• CALL/MILL, CUT0.52, SPIN600, FEED3.0, CLNTON
• TURRET/6
• CALL/MILL, CUT0.5, SPIN900, FEED2.0, CLNTON
• SPINDL/0
• COOLNT/OFF
• END
• FINI

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Other Part Programming Languages

• ADAPT (ADaptation APT) was the first attempt to
  adapt APT programming system for smaller
  computers
• AUTOSPOT (AUTOmatic Sytem for POsitioning Tools)
  was developed by IBM and first introduced in 1962
• EXAPT (EXtended subset of APT) was developed
  jointly in German in about 1964 by several
  universities to adapt APT for European use. It is
  compatible with APT and thus can use the same
  processor as APT
• COMPACT was developed by Manufacturing Data
  Systems, Inc. (MDSI)
• SPLIT (Sundstrand Processing Language Internally
  Translated) was developed by Sundstrand
  Corporation, intended for its own machine tools
• MAPT (Micro-APT) is a subset of APT, to be run on
  the microcomputers

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